Lithographic digital printing plates are imaged on special opto-mechanical plate setters. The imaged plates undergo a chemical development stage and this process is usually performed by a plate developing processor device. The development process uses chemical development material in a liquid form. The material is filled into the developer section tank 104 within the plate processor device, as shown in prior art FIG. 1.
After a lithographic plate is imaged, it is be transported through the plate processor device for processing, consuming a portion of the development liquid in developer section tank 104. The developer liquid 108 inside developer section tank 104 should be maintained at fixed level. In prior art devices, the fixed level is maintained by the use of a float sensor 112, which floats on developer liquid 108, to indicate the level of the developer liquid. After each plate development cycle, new developer liquid is replenished from fresh developer container 116 via developer replenish pipe system 124. The new developer material from fresh developer container 116 will flow into developer section tank 104, maintaining the developer liquid 108 level. In order to keep developer liquid 108 level fixed, part of the developer liquid from developer section tank 104 will be drained into the developer waste container 120, via developer waste overflow pipe system 128.
The invention disclosed hereunder, proposes a more accurate measurement apparatus and method in order to keep the level of developer liquid 108 at a fixed level, which is necessary for achieving reliable results during plate development process.